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High impact mass drops from helicopter: A new active seismic source method applied in an active volcanic setting
Author(s) -
Jolly A. D.,
Chardot L.,
Neuberg J.,
Fournier N.,
Scott B. J.,
Sherburn S.
Publication year - 2012
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/2012gl051880
Subject(s) - impact crater , volcano , geology , seismology , attenuation , traverse , ejecta , seismic wave , geodesy , physics , quantum mechanics , astronomy , supernova , optics
We obtain estimates of the seismic velocity and attenuation for White Island volcano by use of high‐impact sand‐bag drops from helicopter. Three drops were attempted, two at either end of a 6‐station linear array within the crater floor, and the third in the volcano's crater lake. The bags were dropped from ∼310–380 m height and contained ∼700 kg of sand. The impact velocity was estimated at ∼60–70 m/s yielding a kinetic energy of about 10 6 Nm, giving P ‐wave onsets to a distance of ∼1 km. We obtained a seismic velocity estimate of Vp = 1.2 km/s for the unconsolidated crater floor and Vp = 2.2 km/s for rays traversing through consolidated rock outside the crater. Attenuation was very strong ( Q < 10) for both consolidated and unconsolidated parts of the volcano. This trial shows that low cost helicopter mass drops can be successfully applied to safely determine sub‐surface properties at hazardous volcanoes.